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By J. A. Scott, K. Moreau, H. Shang

"Trials of automated technology at underground mine sites around the world have reported increased production and the potential for lower energy consumption. Autonomous mining eliminates a range of delays related to operator downtime and travel to the workface and facilitates continuous operation in conditions that are unsafe for workers. Automation also introduces complexities and safety hazards arising from equipment–personnel interactions; automated processes must be isolated from other stope-cycle–related activities such as production drilling, development, loading, and backfilling, poten¬tially requiring changes to the mine design to maintain an efficient and safe operation. This paper reviews and discusses the implementation of automated equipment in deep underground mining operations and the challenges and advantages associated with the technology. ¦ KEYWORDS Automated equipment, Emissions reduction, Energy, Productivity, Sustainability, Technology, Underground mines RÉSUMÉ Des essais de technologies automatisées dans des sites miniers souterrains aux quatre coins du monde ont indiqué une production accrue et la possibilité de réduire la consommation d’énergie. L’exploitation minière autonome élimine tout un éventail de retards liés aux temps d’immobilisation des opérateurs et aux déplacements vers le front de taille, et facilite l’exploitation continue dans des conditions qui s’avèrent peu sécurisées pour les travailleurs. L’automatisation introduit également des complexités et des risques pour la sécurité, qui surviennent en raison des interactions entre l’équipement et le personnel. On recommande d’isoler les procédés automatisés des autres activités liées au cycle des chantiers telles que le forage de production, le développement, le chargement et le remblai, ce qui pourrait entraîner des changements au niveau de la conception de la mine afin de préserver rendement et sécurité dans l’exploitation. Cet article examine et aborde la mise en oeuvre de l’équipement automatisé dans des exploitations minières souterraines profondes, ainsi que les enjeux et les avantages associés à cette technologie. ¦ MOTS CLÉS durabilité, énergie, équipement automatisé, mines souterraines, productivité, réduction des émissions, technologieINTRODUCTION As the mining industry continues to exhaust easily accessible orebodies, the need for efficient, deep (typically below 2,500 m) mine operations increases (Atlas Copco, 2013a); however, the mining process can become economically infeasible at great depths because operation costs drastically increase. This has resulted in investigations into automating mining operations as the industry strives for improved productivity (Schunnesson, Gustafson, & Kumar, 2009) and ways to remove personnel from hazardous work areas."

Jan 1, 2019

By Marcel Labbé

La largeur de l?armature peut être modifiée selon les besoins du client entre 48 " et 64" de largeur totale, donc 2 sections de 24" à 32". Ceci permet à l?opérateur d?effectuer le démantèlement de l?équipement pour le déplacement dans les endroits restreints. Le déménagement d?un niveau à un sous-niveau devrait se faire dans un quart de travail de 8 heures. L?option de largeur permet au client de choisir un équipement adapté à son environnement de travail (1). La largeur de la table de forage peut être modifiée selon les besoins du client entre 48" et 96". Cette particularité permet une meilleure stabilité, et plus de précision dans le forage (2). Il y a 4 pattes hydrauliques à chaque coin pour la stabilisation lors de forage (3). La table de forage a 360° d?angle de forage sur 3 côtés du transporteur. La table peut sortir de chaque côté du transporteur de 40 ½" à partir du centre du transporteur pour faciliter la mise en place de la foreuse dans les endroits difficiles d?accès. La plage de forage est considérablement agrandie. Cette caractéristique qui fonctionne hydraulique, permet à l?opérateur de forer sans être obligé de changer la position du transporteur pour des changements de trous. Tous les types de foreuse peuvent être installés sur cette table de forage (4). Sa petite dimension lui permet d?accéder, par des monteries de 30" de diamètre, à des sites de travail de 2,5 mètres de hauteur et largeur. C?est un équipement adapté aux gisements filoniens. Ce genre de gisement est de moins en moins rentable pour les compagnies minières. La mécanisation des ces gisements va permettre de les rentabilisés en augmentant la productivité et la santé du travailleur, en réduisant la dilution (5). Les manettes de contrôle de la foreuse, les mouvements de la table de forage ainsi que le déplacement du transporteur ont été installés selon les recommandations d?un ergonome. Des recherches ont été effectuées par ce spécialiste sur les cas d?accident survenus avec l?utilisation de ce genre d?équipement. Il a déterminé les positions le plus confortable que l?opérateur doit prendre pour éviter les douleurs prolongées (6). Le système de roulement est composé de 4 roues pleines installées sur 4 planétaires de 9000 à 15000 livres de capacité munis chacun d?un moteur hydraulique. Des freins ont été installés sur les planétaires pour assurer la sécurité de l?opérateur et faciliter le positionnement du transporteur lors du forage. Des roues rétractables peuvent être installées pour faciliter l?accès sur rail (7). Ce transporteur peut être alimenté par une puissance électrique plutôt que par une puissance pneumatique. Cette puissance électrique est fournie par un Power Pack qui transforme l?énergie en puissance hydraulique. Ce type d?alimentation est employé lors du forage de développement, mais il peut aussi être utilisé pour le forage long trou. Cet avantage permet au client qui a un problème de pression d?air d?utiliser l?électricité. Par contre si vous utilisez l?électricité mais que dans un secteur isolé le gros courant électrique n?est pas accessible vous pouvez utiliser votre équipement en utilisant la puissance pneumatique. Le changement d?alimentation énergétique se fait facilement (8). Cet équipement est construit pour effectuer 4 types d?activités : forage de développement de niveau et sousniveau avec l?installation d?un bras porteur, forage et pose de câbles d?encrage pour soutènement de terrain, forage de production long trou et forage de monterie ascendante et descendante. L?avantage est que vous investissez dans un seul équipement au lieu de 2 ou 3. Cet avantage vous fait économiser dans votre budget d?équipement. En plus cet équipement est construit pour de dure travaux et ne contient aucun système électronique (9).

May 1, 2001

By Jacek Paraszczak

L?exploitation rentable des gisements de type filonien constitue un problème important dans le contexte actuel de l?industrie minière québécoise. Les études effectuées depuis 1994 ont indiqué, que la technologie d?abattage mécanique utilisant l?outil hydraulique appelé « éclateur radial-axial » constitue une alternative intéressante par rapport aux méthodes conventionnelles par le forage et sautage. Les essais du prototype de l?éclateur ont prouvé qu?il est en mesure d?abattre les roches dures dans un environnement minier, mais sa performance dans les termes de masse du roc abattu dans une unité de temps a soulevé certaines doutes. Pour cette raison, une étude de préfaisabilité de l?éclatage en tant qu?une technologie d?excavation souterraine a été réalisée. Cet article présente quelques résultats des travaux effectués dans le cadre du contrat octroyé à l?Université Laval par le Ministère des ressources naturelles du Québec. Leur objectif principal consistait à comparer, pour les conditions des gisements filoniens, la productivité et les coûts des méthodes d?exploitation souterraine utilisant l?éclatage par rapport à celles conventionnelles. Deux variantes proposées de cette méthode ont été comparées avec la méthode conventionnelle sur le plan du coût (par tonne de minerai) et de la teneur de coupure de minerai d'or. Les études ont démontré que l?application de l?éclatage représente un potentiel de réduire ce coût, surtout dans les situations où l?abattage sélectif pourrait avoir lieu. Pour le cas de base on a trouvé, qu?il serait possible de réduire la teneur de coupure par la marge d?environ 16 ? 26%. Toutefois, les études de sensibilité ont démontré, que le coût dépend de façon important de la productivité d?éclatage, qui, pour sa part, varie beaucoup en fonction de paramètres du massif rocheux devant être abattu.

Oct 1, 2001

By Gordon T. Austin

The combined production value of natural abrasives, which consist of tripoli, special silica stone, garnet, staurolite, and emery, increased in 1987. The increase was, in certain cases, because the materials were used in nonabrasive applications, such as the increased use of tripoli as a filler and special silica stone material as a special-purpose crushed stone. The increased use of garnet as a blasting media accounts for most of its growth. Production and sales of garnet were at a record-high level in 1987. [ ]

Jan 1, 1989

By S. Y. Tshipeng, A. T. Kaniki

"RÉSUMÉ La lixiviation acide d’un minerai oxydé cupro-cobaltifère en milieu non réducteur et en milieu réducteur en utilisant le Fe2+ et le métabisulfite de sodium (SMBS) a été étudiée et les résultats ont été comparés. Les tests de lixiviation ont été effectués à température ambiante, dans une pulpe à 30 % solide, avec une vitesse d’agitation de 600 tr/min, un potentiel redox de 350 mV pour les tests en milieu réducteur, et un pH de 1,8. Les tests de lixiviation avec usage du SMBS comme réducteur ont donné la meilleure cinétique de lixiviation du cuivre. Pour le cobalt, c’est l’usage du Fe2+ qui a donné la meilleure cinétique de lixiviation. L’augmentation de la dose du fer dans la solution au-delà de 5 g/L a influencé négativement les rendements de lixiviation du cuivre et du cobalt. ABSTRACT Acid leaching of a copper-cobaltiferous oxide ore in a non-reducing environment and in a reducing environment using Fe2+ and sodium metabisulfite (SMBS) was studied and the results compa¬red. The leaching tests were performed at room temperature, in a 30% solids pulp, with a shaking speed of 600 rpm, a redox potential of 350 mV for the tests performed in the reducing environment, and a pH of 1.8. The leaching tests using the SMBS as a reducing agent produced the best copper leaching kinetics. As for cobalt, the best leaching kinetics was achieved using Fe2+. An increase in the amount of iron in the solution above 5 g/L negatively influenced copper and cobalt leaching yields. INTRODUCTION La République Démocratique du Congo (RDC) est un pays reconnu dans le monde pour son sous-sol qui regorge d’énormes quantités de cuivre et de cobalt (USGS, 2014; Palisade Research, 2016). La technique qui semble être la plus recommandée pour extraire à la fois le cuivre et le cobalt des minerais oxydés cupro-cobaltifères est la lixivia-tion acide en milieu réducteur. Cette technique est appliquée par la majorité des sociétés minières qui exploitent ces minerais dans l’ex-province du Katanga en RDC, à savoir: Tenke Fungurume Mining, Mutanda Mining, Kamoto Cop¬per Company, Sicomines, Gécamines, Boss Mining, Chemaf, Ruashi Mining et Somika. L’usage d’un agent réducteur est indispensable pour l’obtention d’un bon rendement de lixiviation du cobalt. En effet, plusieurs chercheurs s’accordent sur le fait que le cobalt trivalent de l’hétérogénite (CoO·2Co2O3·6H2O) est insoluble à l’action de l’acide seul; il ne devient soluble qu’après réduction en cobalt bivalent (Mwema, Mpoyo, & Kafumbila, 2002; Mulaba-Bafubiandi, Ndalamo, & Mamba, 2007; Ferron, 2008; Seo, Choi, Kim, & Tran, 2013; Stuurnam, Ndlovu, & Sibanda, 2014)."

Jan 1, 2018

By Gordon T. Austin

The combined value of production of natural abrasives, which includes tripoli, special silica stone, garnet, staurolite, and emery, increased about 9% in 1988. In the case of emery, the increase was due to an increase in unit value of the material produced. The increase in the value of garnet and staurolite production was simply the result of an increase in the quantity of materials produced. However, special silica stone experienced both an increase in unit value and quantity produced. The nonmetallic manufactured abrasives industry, which includes only silicon carbide and fused aluminum oxide in the reported statistics, enjoyed the best production year since 1981 in terms of total quantity produced. Production increased 22% in quantity and 16% in value com-pared with those of 1987.

Jan 1, 1990

By Isabelle Demers, Audrey Jalce

L’industrie minière génère chaque année une quantité considérable de rejets miniers, principalement sous forme de stériles ou de résidus de l’usine de traitement. Les stériles sont des roches sans valeur économique, excavées pour atteindre la roche minéralisée. Ils sont usuellement empilés en surface formant des haldes à stériles. Les résidus miniers sont des roches finement broyées, mélangées avec de l’eau, résultant du traitement du minerai. Ils sont généralement pompés et entreposés en surface dans des parcs à résidus. Cependant, leur stockage peut être sujet à des instabilités géotechniques, mais également géochimiques, pouvant entrainer des problèmes environnementaux majeurs, tels que le drainage minier acide (DMA). Le DMA se produit lorsque des minéraux sulfureux, contenus dans ces deux types de rejets, s’oxydent au contact de l’eau et de l’oxygène [1]. Le DMA se caractérise par une solution acide (pH inférieur à 6) riche en métaux, contaminant les eaux souterraines et de surface et représentant alors un danger pour la faune, la flore et la santé humaine [2]. La remise en état et la fermeture des sites miniers doivent donc être pensées dès la phase d’étude du projet d’exploitation, afin de proposer une méthode de gestion des rejets qui permettra de limiter les impacts environnementaux pendant et après l'exploitation.

May 2, 2024

By Robert G. Clarke

The production of natural abrasives varied in quantity and value compared with those of 1974. Output of tripoli-type materials and garnet both decreased in quantity and value. Special silica stone products decreased in quantity but in-creased in value. The production of emery increased 38% in quantity. The production of manufactured abrasive materials decreased for all types and the decreases were more in quantity than in value. [ ] FOREIGN TRADE Imports of abrasive materials were 15% less in value than in 1974, and exports plus reexports decreased in value 10%. Net exports, the excess of exports and reexports over imports, were $9.3 million, about four times that of 1974. The volume of all abrasive materials exported decreased and the value of nearly all decreased.

Jan 1, 1977

By J. W. Thompson

AN ACT prescribing the mode of maintaining and defending possessory actions on lands belonging to the United States. The People, etc. SEC. 1. Any person now occupying and settled upon, or who may hereafter occupy and settle upon any of the public lands belonging to the United States, unoccupied, except upon lands containing mines of any of the precious metals, may commence and maintain any action for interference with, or injuries done to his possession of said land, against any person or persons so interfering with or injuring such land or such possession. SEC. 2. On the trial of any such cause, the possession or possessory right of the plaintiff shall be considered as extending to the boundaries embraced by the claim of such plaintiff, so as to enable him to have and maintain any action as aforesaid, without being compelled to prove an actual inclosure; provided, that such "claim" shall not exceed in any case one hundred and sixty acres of land. SEC. 3. Every such claim, to entitle the holder to maintain any action as aforesaid, shall be marked out, so that the boundaries thereof may be readily traced, and the extent of such "claim" easily known, and no person shall be entitled to maintain any such action for possession of, or injury to, any claim, unless he occupy the same, or shall have made improvements thereon to the value of $100. SEC. 4. A neglect to occupy or cultivate such "claim," for the period of three months, shall be considered such an abandonment as to preclude the claimant from maintaining any action as hereinbefore mentioned. Sec. 5. Any person or persons claiming the right of possession to land under this act shall have the right to defend said possession and the claim thereto, and all the rights and privileges given them by this act.

Jan 1, 1918

By Hazel B. Comstock

This materials survey on magnesium and magnesium compounds is one of a series of Bureau of Mines publications designed to serve the needs of Government and industry for comprehensive, up-to-data information on mineral commodities and activities. Magnesium, the world's lightest structural metal, has become a most useful material in airborne and spare vehicles, automotive equipment, machine tools, and consumer products. Use of magnesium ores in basic refractories for iron and steel furnaces has expanded as the production of iron and steel has increased, Progress in converting steel fun cares to the use of oxygen has further increased the use of magnesia and magnesite brick.

Jan 1, 1963

By Hazel B. Comstock

[This material survey on magnesium and magnesium compounds is one of a series of Bureau of Mines publications designed to serve the needs of Government and industry for comprehensive, up-to-date information on mineral commodities and activities Magnesium, the world's lightest structural metal has become a most useful material in airborne and space vehicles, automotive equipment, machine tools, and consumer products. Use of magnesium on in basic refractories for iron and steel furnaces has expanded as the production of iron and steel has increased. Progress in converting steel furnaces to the use of oxygen has further increased the use of magnesium and magnesite brick.]

Jan 1, 1963

It is probably safe to say that, as the economic well-being of the mining industry goes, so goes the fortunes of mineral explorationists. And in 1977 the industry was not well at all. The year-long depression of the copper industry, marked by layoffs, temporary shutdowns, and mine closures, provided an appropriate background for the collapse of the nickel market, passage of a surface mining law that will affect the hard-rock industry in ways that are yet unclear, and the threat of operating under a new set of rules brought on by reform of the Mining Law of 1872.

Jan 5, 1978

By Keith L. Harris

Economic activity in the United States picked up in the third quarter, according to the latest estimate released by the Department of Commerce. Real gross national product (GNP)--the Nation's output of goods and services--grew at a seasonally adjusted annual rate of 4.3%, or $17.6 billion, compared with a rate of 1.9% for the second quarter of 1985 and 1.6% for the third quarter of 1984 (table 1). The 4.3% rate is one percentage point above the preliminary estimate reported in the August/September issue of Minerals and Materials. Most of the upward revision was due to the change in business inventories and Government purchases, while the figure for net exports was revised downward substantially. The 4.3% growth bettered by 1.5% the average rate of growth in GNP from 1974 through 1984 and was 1.1 % above that of the period from 1975 through 1984 and 0.7% above that of 1980 through 1984. Of importance to the minerals industry was the $14.4-billion growth in personal consumption expenditures, $10.2 billion of which was for durable goods (especially domestically produced automobiles) and the growing residential investment. The net export deficit continued to grow, however, and investment in nonresidential structures, producers' durable equipment, and business inventories declined. Prices, as measured by the GNP fixed-weighted price index, increased at an annual rate of 3.1% in the third quarter, compared with 3.9% in the second quarter. The slower rate of inflation resulted mainly from a decline in energy prices, following second-quarter increases. Fourth-Quarter Prognosis Many of the economic data available for October and November indicate that the economy is growing modestly and will continue to grow over the next 3 to 6 months. The composite index of leading indicators, designed to predict economic activity within 3 to 6 months, rose 0.3% in October, the sixth consecutive monthly advance, according to the Department of Commerce. Six of the 11 available leading indicators were positive: Stock market prices rose, as did sensitive material prices, credit outstanding, and manufacturers' new orders for consumer goods and materials; initial claims for unemployment insurance decreased, and firms were getting slower delivery of goods. Four of the indicators were negative: Business formations, homebuilding permits, contracts and orders for plant and equipment, and money supply all declined. The average hours worked per week, already at a high level, remained unchanged.

Jan 1, 1985

By Gordon T. Austin

The combined value of production of natural abrasives, which includes tripoli, special silica stone, garnet, staurolite, and emery, increased about 21070 in 1989. The increase in the value of staurolite and tripoli production was the result of an increase in the quantity of materials produced and an increase in the unit value. Emery decreased due to the significant decline in the volume of the material produced. Special silica stone experienced both a decrease in unit value and quantity produced. Garnet showed a small increase in quantity, but a decrease in unit value. The silicon carbide industry saw a slight decrease in the quantity produced and a 12070 increase in the value of production. The fused aluminum oxide industry showed a 5070 decline in the quantity produced, but enjoyed a 15070 increase in the value of production. Combined production for both industries decreased 4070 in quantity but increased 13070 in value compared with those of 1988.

Jan 1, 1991

The contribution of minerals to the growth and development of the United States is best demonstrated by the uses which have evolved during the past two centures. During pre-Revolutionary days the colonies were essentially agricultural in character, producing cotton, tobacco, rice, indigo, grains and flour, fish, livestock, dairy products, and timber. Shipbuilding was the major manufacturing industry. In 1763, the total value of exports for Virginia, Maryland, New York, Pennsylvania, and Massachusetts was £2,722,000, of which £55,000, or 2 percent, was for "copper ore, and iron in pigs" (3)1 and £49,000 was for 21,000 barrels or hogsheads of "pot-ash." The value of 75 ships built for sale in 1763 by the colonies was £61,500.

Jan 1, 1976

By J. Bélanger, B. Semlali, M. Grenon

RÉSUMÉ La conception des fosses ainsi que l'évaluation des ressources géologiques et des réserves minières sont désormais réalisées entièrement à l'aide d'outils informatiques spécialisés. Cependant, plusieurs analyses, pourtant essentielles à l'évaluation de la viabilité du projet, sont réalisées en parallèle sans véritable optimisation ni synergie avec l'ensemble des données disponibles. Cet article présente deux approches permettant d'intégrer certains types d'analyses aux modèles de blocs miniers. Ces approches permettent de quantifier la broyabilité du massif rocheux ainsi que d'étudier la stabilité des pentes minières à même les outils d'optimisation et de planification minières. Cette méthode permet dès l'étude de faisabilité d'un projet minier de maximiser les données disponibles, menant ainsi à une approche plus intégrée en conception minière. De plus, ces approches sont flexibles et permettent d'évaluer rapidement plusieurs scénarios, tout en laissant la possibilité de bonifier le modèle et de revoir la conception tout au long du projet minier.

Jan 1, 2010

By Charles W. Merrill

THE INDUSTRIAL strength and the security of the United States require an adequate, dependable, and continuing supply of raw materials, of which minerals constitute an indispensable segment. With an expanding population, a rising standard of living, and the instability inherent in a constantly changing international situation, the mineral supply outlook is a major national concern. Structures, roads, and machines are built largely of mineral products; the energy to heat the structures and to power the machines is derived mostly from minerals; agricultural out-put is sustained with the aid of mineral fertilizers; and the Nation's economic and military security both are founded ultimately on its ability to obtain and utilize essential metals, nonmetals, and mineral fuels.

Jan 1, 1965

By Keith L. Harris

Buoyed primarily by growing consumer spending, the economy rebounded from a weak second quarter. According to preliminary estimates released by the Department of Commerce, real gross national product (GNP) grew $2 1.9 billion during the third quarter, producing a seasonally adjusted annual growth rate of 2.4%, compared with a rate of 0.6% in the second quarter of 1986 and 4.1% for the third quarter of 1985 (table 1). Third-quarter real personal consumption expenditures and Government purchases of goods and services rose $42 billion and $7 billion, respectively, but those gains were partially offset by the continuing decline of gross private domestic investment, off $16 billion, and the growing trade deficit, up $11 billion. Three quarters of the growth in consumer spending occurred in the durable goods sector as consumers responded to discounted financing offered by automobile manufacturers attempting to lower inventories of 1986 vehicles, Increased purchases of other durable goods, such as furniture and home furnishings, also contributed to the strength of the durable goods sector. The success of the automobile inventory reduction program as well as weak factory output led to a $20 billion decline in inventory growth. Investment for housing and producers' durable equipment expanded, however, and mitigated some of the impact of slower inventory depending on gross private domestic investment, Capital spending for nonresidential structures declined for the third consecutive quarter. The declining capital spending and the growing trade deficit continued to be significant and interrelated problems for the economy. Real capital spending for new plants and equipment during 1986 is expected to decline 2.5% after rising 8.7% in 1985 and 15.8% in 1984 (table 2). It is likely that capital expenditures bottomed out in the second quarter and that they will expand in the third and fourth quarters. The first-half decline was partially attributed to uncertainty arising from the pending tax- overhaul bill. Furthermore, there is little impetus for corporations to invest in new capacity since factories are operating at less than 80% of capacity (table 3) largely because of the continuing growth of imports. The growth rate of the trade deficit dropped sharply in the third quarter to less than half that of the previous quarter. Low oil prices, declining auto- mobile and steel imports, and increased exports of agricultural goods contributed to this decline. The continued low growth of the economy caused the Federal Reserve System to reduce the discount rate for the fourth time this year (in late August), drop ping it to 5,596, the lowest level in about 9 years. Inflation, as measured by the fixed- weighted GNP price Index, continues to remain low, but rose from the revised second-quarter level of 1.7% to 2.596, mostly because of rising food costs.

Jan 1, 1986

The Black Hills Mineral Atlas briefly summarizes all important data available on the mines and mineral deposits in the Black Hills that have been explored, developed, mined, or located. The purpose of the atlas is threefold; First, from available data the general potentialities of the Black Hills region can be determined, although it is not possible to calculate actual ore reserves; second, it will provide the necessary basic information regarding a given property or commodity for further detailed study; and third, the compilation is a comprehensive directory of Black Hills deposits.

Jan 1, 1955

By Albert H. Fay

This glossary is published by the Bureau of Mines as a contribution to the mining literature in the belief that it will fill a long-felt need. It contains about 20,000 terms; these include both technical and purely local terms related to metal mining, coal mining., quarrying, petroleum, and natural gas, and metallurgical works; names of useful, important, and common minerals and rocks; and geological terms. It presents in one comprehensive volume the available standard, technical terms relating to the mining and mineral industry, as well as provincialisms that have been or are now in use in English-speaking countries. The glossary also includes many terms relating to ceramics and. the clay industry, glass making, foundry practice, railway and building construction, electrical installation and power-plant equipment, and chemical terms relating to metallurgical practice. Complete lists of terms for each of these allied industries are beyond the scope of this glossary. Paleontological terms, although closely associated with geology, are far removed from mining and metallurgical operations, and for this reason have been omitted.

Jan 1, 1920